1. Field of the Invention
This invention relates to the field of microwaves More particularly, the invention relates to dielectric resonator oscillators for use as microwave frequency sources.
2. Description of the Prior Art
One of the most critical problems confronting designers of high-precision RF and microwave systems, such as compact radars, beacons, transponders, satellite communication systems, atmospheric profilers and electronic countermeasure receivers, has been the generation of high-frequency signals of extremely good spectral purity. Dielectric resonator oscillators (DROs), used in such equipment for microwave signal generation, have been shown to have extremely low-phase noise and high-temperature stability. Prior art DROs are described by G. K. Montress and T. E. Parker in "Design Techniques for Achieving State-of-the-Art Oscillator Performance", Proceedings of the 44th Annual Symposium on Frequency Control 1990, pp. 522-535, IEEE Catalog No. 90CH2818-3.
Typical DROs include a dielectric resonator, used as a frequency determining circuit element in a parallel feedback configuration with an amplifier. Feedback oscillators are of particular importance because they usually offer much better FM noise performance and frequency stability than achievable with conventional reflection oscillators. Additionally, dielectric resonators have found extensive use because they offer high efficiency and simple construction. However, although such prior art DROs have served the purpose, those concerned with their development have long recognized the need to further lower their cost, increase their temperature stability and improve their phase-noise performance. The present invention fulfills this need.